Coda group

Tube Characterization Scans (Freeman)

Introduction

In order to find the proper threshold, our first run, we adjusted the threshold on the "discriminator card". The next 4 sets of scans we adjusted the voltage and then let coda run for a fixed amount of time (600 s). This gave us some event count. By plotting the log(Rate) vs. Voltage we are able to characterize each tube and find at which voltages we get all noise and for which voltages we get peak signal.

Scans

Run Plans and Discussion

Rate vs. Threshold Measurements

Our original plan was to scan through thresholds 100mV - 2000mV at 100mV steps and used a voltage of 1550 V . We began by adjusting the threshold, then let coda run for 1000 events. We recorded the start and stop time of coda. From this we are able to extract a time delta, and then calculate a rate.

We found very quickly that as we increased the threshold from 100mV, 200mV, and then 300mV that if we continued to use 1000 events it would take many hours to complete the upper thresholds. We decided to lower the amount of collected rates to 250 events. Equally as we raised the threshold to higher values we found that cutting off the max threshold was a good idea. We plotted and fit our data after we found the first few points. This allowed us to see an exponentially decreasing plot. With a threshold of 500mV we have, nearly, a zero rate. We decided to not go to any higher thresholds, but to fill in some of the gaps and took more data points from 150mV - 450 mV By plotting the log(Rate) vs. Threshold we were able to see a plot that has a linearly decreasing slope, roughly picking where the line crosses the y=0 we chose a threshold of about 250mV.

Rate vs. Voltage Measurements

Original plan was fix the number of rates such as was found in the threshold scans, this proved to be cumbersome. We eventually change to a fixed number of time 600s and then got then allowed coda to collect events.